Typically previous limited slip differentials have an input element, two output elements, two output shafts associated each with one of the output elements, and axially displaceable means such as disk or cone clutches for the purpose of coupling together, by their axial displacement, two of the three input and output shafts.
This axial displacement can include spring means to take-up play within the clutch, however, the essential operating parameter is not the displacement itself but the force applied to the coupling means. The result of this coupling, which can be total or partial depending on the means used, is that when the resistive torque at one of the outputs decreases, the input torque is shared equally between the two outputs.
Typical of the numerous prior art patents relating to limited slip differentials are U.S. Pat. No. 3,457,807 Altmann; U.S. Pat. No. 3,546,968 Altmann; and U.S. Pat. No. 3,906,812 Kagata. Both Altmann differentials as well as Kagata are of the type wherein a clutch applying force is through springs with the spring force being opposed by the resistive torque of the output shaft. In the Altmann patents the springs provide the sole clutch applying force. This basically is the same operation in Kagata in that either the sole or controlling clutch applying force is through springs. Kagata has a modification in which a cam device comes into play after the spring has actuated the lock-up clutch to provide an added force to help hold the clutch in engagement.